THE EFFECT OF DRIP LINE PLACEMENT ON SOIL WATER DYNAMICS IN THE CASE OF SURFACE AND SUBSURFACE DRIP IRRIGATION

The effect of drip line placement on soil wetting pattern, deep percolation and evapotranspiration, in the case of surface and subsurface drip irrigation, was considered. To this aim, a mathematical model which describes water flow under surface and subsurface drip lines, taking into account root water uptake, evaporation of soil water from the soil surface and hysteresis in the soil water characteristic curve θ(Η), was used. Several numerical experiments were conducted, for three soils, two discharge rates and four drip line placements. The results showed that when the depth of placement increases, the horizontal movement of water, close to the surface, decreases. It was also concluded that in the case of surface drip irrigation, the values of the water content close to the drip line are lower compared with those of subsurface drip irrigation. Lastly, the numerical results showed that deep percolation increases at a higher pace than evaporation decreases, resulting in lower values of irrigation efficiency as the depth of placement increases. Copyright © 2012 John Wiley & Sons, Ltd.